We had to make it up as we went.
The new generation of American middle-grade graphic novels had just started. There were a few books from Scholastic--graphic novel versions of GOOSEBUMPS, and the Babysitters Club, as well as reprints of Jeff Smith's BONE series. Kazu Kibiushi's first AMULET: The Stone Keeper had just come out. And BABYMOUSE was just two or three books along. All of those books were totally different sizes. See here:
Scholastic's books were somewhere between the American and European size--but many of them were black and white (like Manga). Scholastic learned pretty quickly that kids wanted COLOR. The BONE reprints, originally done in black and white, were soon brought out in color versions. BABYMOUSE was Manga-sized, black and white, but with one extra color (pink!). Amazingly, the one extra color worked! It worked so well, in fact, that many middle-grade graphic novels have since followed that format: Lunch Lady, Dragonbreath, and a little series you might have heard of called Hazardous Tales.
So, before we started Rapunzel, we had to decide what size the book would be--and if it would be in color. After finishing the inks, I admit, I sent an email requesting the book be black and white. Can you imagine Rapunzel's Revenge with no color? Size-wise, I wanted to go as big as possible--having long been a fan of the super-sized European-style comics (think Tintin and Asterix). Shannon and Dean's script had a lot to say, and I had a lot of scenery I wanted to draw. We went as big as the publisher allowed: not quite as big as the Europeans, but a bit larger than the Scholastics titles.
We went full color, bigger and thicker than a standard American comic book, but not quite as thick as a Manga. Essentially, we created our own new size and format--a size and format nobody else was using.